u can use urpmi to update packages or install new ones..but seriously...you might want to read over some documentation before using it...i managed to fubar up my Mdk using it to update gnome....
here are few commands from what i remember
urpmi.update -a
this will update all your package list (ur media)
u can select to upgrade and install everything from your new list by
urpmi --auto-select
if u want just want to install everything with let's say gnome in the name then
urpmi gnome -a
or if u just want to select a package and install package one by one which i don't recommend since this is how i fubared my mdk just type in
urpmi gnome
then it will list all the packages with gnome in the name then just type in
urpmi *package name from the list*
also if u want to add new source (media) to urpmi try this link
http://plf.zarb.org/~nanardon/urpmiweb.php
this will generate the code for you for easy adding of a new source
hope this helped